This invention relates to a catalytic process of reforming an alkyleneamine feedstock, such as diethylenetriamine or higher molecular weight polyethylenepolyamines, to an alkyleneamine product or mixture thereof which is different from the feedstock.
Alkyleneamines, such as non-cyclic polyalkylenepolyamines, find utility as dispersants, surfactants, chelants, catalysts, curing agents, extenders in polyurethanes, and as starting materials in the preparation of pesticides.
It is known that non-cyclic polyalkylenepolyamines can be prepared by the reaction of an alkyl halide with ammonia or an amine. The product is a polyalkylenepolyamine hydrohalide salt, which must be neutralized with base in order to recover the valuable polyalkylenepolyamine product. The neutralization produces a waste stream of metal salt which must be disposed. Moreover, the process produces considerable amounts of cyclic products.
Certain patents teach the reforming of alkyleneamines, such as ethylenediamine, directly to non-cyclic polyalkylenepolyamines. For example, U.S. Pat. No. 4,316,841 discloses a process wherein ethylenediamine is reformed to higher molecular weight non-cyclic homologues, such as diethylenetriamine. Diethylenetriamine, on the other hand, is taught to be reformed to a mixture of higher and lower molecular weight ethylenepolyamines. The catalyst for this process is boron phosphate, a phosphate of a Group IA or IIA metal, or a phosphate of zirconium, antimony, tin or iron. Typically, these catalysts are soluble in amines and water. Consequently, the catalysts leach into the reaction mixture causing catalyst losses and separation problems.
Likewise, U.S. Pat. No. 4,316,840 discloses a process for the reforming of alkylenepolyamines in the presence of a catalyst comprising a metal sulfate or nitrate wherein the metal is selected from the group consisting of Groups IA and IIA metals, as well as zinc, zirconium, antimony, iron and tin. Ethylenediamine is taught to be reformed into polyethylenepolyamines. Diethylenetriamine is taught to be reformed into higher and lower molecular weight ethylenepolyamines. Large amounts of cyclic products, such as piperazine, are simultaneously produced. Typically, these catalysts are also soluble in amines and water. Consequently, catalyst leaching and separation problems are also inherent in these processes.
U.S. Pat. No. 4,568,746 teaches a process of reforming ethylenediamine in the presence of a catalyst containing nickel, cobalt or rhodium. Likewise, U.S. Pat. No. 4,625,030 teaches a process of contacting ethylenediamine in the presence of hydrogen with a catalyst comprising nickel impregnated or coated together with iridium or platinum on a support of silica-alumina to produce predominantly diethylenetriamine. Disadvantageously, these processes are limited to a narrow, low molecular weight product liner such as diethylenetriamine, and do not produce valuable higher homologues. Moreover, processes like these which employ hydrogenation catalysts require an expensive noble metal and further require hydrogen.
U.S. Pat. No. 3,956,329 discloses the deammoniation or cracking of an alkyleneamine, such as diethylenetriamine, over a zeolite catalyst containing at least one cation selected from the alkali metals, the alkaline earth metals, zinc group elements, or hydrogen or ammonium cations. The predominant products are cyclics, such as, triethylenediamine and piperazine.
U.S. Pat. No. 4,547,591 discloses the preparation of predominantly linear polyethylenepolyamines by reforming ethyleneamines in the presence of a silica-alumina catalyst, optionally containing an acidic phosphorus cocatalyst. Large amounts of cyclic products, such as piperazines, are simultaneously produced.
In addition to the specific disadvantages noted hereinabove, the aforementioned processes of the prior art are inflexible and cannot be tailored to meet changing market demands. For example, suppliers may find that at one time the market demands non-cyclic polyalkylenepolyamines, while the demand at another time may be for cyclic products. Moreover, within the broad demand for non-cyclic or cyclic products, the market may demand large supplies of one particular product and small supplies of another product. For example, the market need for non-cyclic triethylenetetramines and tetraethylenepentamines may exceed the need for mixtures of higher molecular weight non-cyclic polyethylenepolyamines, or vice versa. Cyclics, such as aminoethylpiperazine, may be valuable, whereas piperazine may be less so. Individually, the processes of the prior art cannot handle such broad needs.
It would be desirable to have a process which employs an inexpensive catalyst which is capable of directly reforming an alkyleneamine feedstock to a more valuable alkyleneamine product or mixture thereof which is different from the feedstock. It would be more desirable if the catalyst is insoluble in amines and water so as to avoid catalyst losses and separation problems. It would be even more desirable if the process does not require hydrogen gas or an expensive noble metal. Finally, it would be most desirable if the process is flexible and could be controlled to produce high yields of non-cyclic alkylenepolyamines or cyclic products, as desired.